It would be hard to advise unless you had more direct knowledge of the people and the situation, and whether the dom just gets off on abusing his power over the subs or whether he is just inexperienced at how to manage the relationship.
My general advise for ALL relationships, maybe especially in polycules and dom/sub situations would be to have a periodic "Out of Character" honest discussion of the relationship, what things are working well, what things are not working well, and work together to find a way to get everyone's needs met.
I think if the dom had the wisdom and capacity to sit down and do a meeting like this with his subs, they could establish clear boundaries of what things are fun ways for the dom to push his authority/power over the subs, but also how to allow the subs ways of providing boundaries and "soft no" without having to resort to safe words, mutual action, or leaving the relationship.
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